Invention Prototype Makes Quick Work of Tree Pruning

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An inventor in Oregon is developing a new, selfpropelled tree pruning machine that, if successful, could make pruning trees more economical for woodland owners. While pruning of commercial species like Douglas fir in fully-stocked stands is starting to catch on, it is of particular importance in silvopastoral and alley cropping regimes where trees are initially planted at wide spacing. Timely pruning increases the volume of knot-free clearwood and improves the market price that agroforest owners can realize at harvest.

John Clouston, owner of Clouston Hydraulics in Junction City, OR, demonstrated a prototype of the “Tree Shaver” during a field day at the Melcher Tree Farm near Sweet Home, OR. (Mike and Glenda Melcher were recognized as the 1998 Oregon State Tree Farmers of the Year by the American Tree Farm System). John’s son Leroy Clouston, company sales manager, helped demonstrate the machine.

Currently in its second prototype, John plans to make more improvements before the machine will be commercially available. He has received patents on the basic design. John already holds a patent on a hydraulic machine he invented that is used in plywood manufacturing. He said that he started thinking about developing a tree pruning machine over six years ago, and created the first prototype in 1997.

The “Tree Shaver” appears to be an improvement over other self-propelled pruning machines that are now on the market, such as the “Tree Monkey” or “Tree Witch.”. According to John, it will prune a tree up to 27 feet above ground and return in 2 minutes or less. That represents a significant speed advantage over manual methods that rely on ladders and saws.

The unit is powered by a chainsaw engine driving four small rubber tires that rapidly propel the machine as it spirals up the tree. Instead of a flat cutting blade that can bind, the “Tree Shaver” uses a round mill end (side-cutting) bit to quickly cut limbs up to several inches thick. An on-board air compressor powers the pneumatic gripping system which maintains a constant grip on the tree as the machine ascends along the decreasing diameter of the stem. The engine throttle and grip strength can be adjusted by radio remote control, allowing the operator to control pruning on each tree, compensate for heavy branches or wet bark, and stand clear of falling limbs. Stub length can be manually adjusted.

The current design of “Tree Shaver” can prune trees 3.5 to 11.5 inches in diameter, John said. This would make it useful for the second and third pruning “lifts” after initial training and pruning is accomplished from the ground by manual means. As many as 30 trees can be pruned up to 27 feet above ground on one tank of gas, he said. A two-person team is required to move and operate the machine which consists of two halves, weighing a total of 100 pounds, that are fitted together around the base of the tree. John said that he hopes to increase the horsepower and reduce the weight of the next prototype, so that only one operator is required.

The “Tree Shaver” has so far been tested on Douglas fir and hybrid poplar, and John said he would like to test it on black walnut and other commercial species. He said that the current model works best on straight-stemmed trees without large forks or bulges at branch nodes, e.g. not like radiata pine.